Signor to vigkers limited



June 19, 1928. 1,674,333

' F. G. JOHNSON TIME FUSE FOR PROJECTILES Filed July 19, 1927 Patented June 19, 1928.

remas- FBEDERICK GEOFFREY LEES JOHNSON, OF WESTMINSTER, LONDON, ENGLAND, AS- SIGNOE TO VICKERS LIMITED; OF \NES'IMlNSTER, ENGLAND.

TIME FUSE For PROJECTILES.

Application filed July s, 1927, Serial no; 206,828, and in Great Britain June 17, 1926.

t This invention relates to projectile time fuses of the kind having a chamber or dome intowhich pass the gases resulting from the burning of the time ring or fuse composition and from which the gases pass to the atmosphere through one or more small holes.

The chief object of the present invention is to provide an improved construction of fuse takes place through a suitably shaped nozzle the outer end of which is subjected to a suction effect during the flight of the pro jectile'such that a certain ratio between the pressure at the outer end of'the nozzle and the inner end of the nozzle (i. e. the interior of the chamber) is produced, this ratio bee ing belowthat which is known to give the maximum velocity of flow through the nozzle, and the size of the nozzle is so chosen that at this maximum velocity the gases generated (or as much of the'gases as is not condensed in .the chamber) willfescape as fast as they are generated so that the pressure in the chamber will remain substantially atmospheric. In the preferred constructional form of theinvention the. aforesaid chamber is'constituted by a cap mounted in front of the adjustable time ringand the nozzle is arranged at the front end of this cap co-axially with, respect to the axis" of the shell so as to avoiddisturbances .due to the rotationi'of the shell.

1 In order that the said invention may be clearly understood and readily carried'intov effect the same will now be described more fully with reference to the accompanying drawings, in which r :Figure 1 1s. an axial section shewing a fuse constructed according to the invention,

the time ring beingset to the safety position. V a a.

Figure 2 is a section taken approximately on the line 2, 2 of Figurel,

Figure 3 an underneath plan of the time ring shewing the fusecomposition therein,

Figure l is a sectionalelevation viewed k3 from the left of Figure 1, Y

Figure 5 is a section taken approximately on the line 5, 5 of Figure 2, I Figure 6 is a section taken approximately on the line 6, 6 of Figure 2, gigure 7 is an enlarged view of the nozzle, an

Figure 8 is a viewYsimilar to Figure 1 shevving the fusewith a percussion ignition device addedil A is the fuse body 'carrying the' usual magazine A and powder pellets A A leadingto the'latter, B is'the adjustable time ring rotatably mounted/u'pona forwardly extending and axial stem A of the fuse body A and held in place by a nut B and a spring 13 C is the cap forming the aforesaid chamber, this cap carrying a plug D. formed with the nozzle D and also carrying a screw-threaded noseqE which holds the plugin position and the further purpose of which will be explained later.

In the exampleshewn'the time ring B car .ries the time ignition: pellet b whichfon shock-of dischar e, sets'back'to bring the detonator cap. against the needle I)? as is. well understood. When the time ring is set to "any but the safety position the flash from the" cap '5 passes through a hole 6 and ignites the-"end b of the fuse composition carried by a chan-nel'in the ring B, this composition burning towards the other end 12 until the pellets A A leading to the magazine A are ignited. As the ignition device 7), 6 bi is'carried by the time ring Bth'e fuse composition is always ignited at. the end 6 so that there is: only one surface burning atone time and in con-' sequence there is a"'p'ract-icallyconstant rate of evolution 'of' gasfrom the burning "com;

pos tion which isimportant for the success-f ful functioning of theinvention.

' Closetothe' end I)?" of the fuse compost" tion thering B has a holed); leading'into" the interior of the cap C sothat the gas as it is evolved: from the 'fuse composition enters the said interior and passes to' the atmosphere through the nozzle D in the plug D, through a central recess E in the nose E and through holes 6, ein this nose. The said holes are rearwardly directed'as she'wn and termlnate at their outer ends 111 an annular recess E in the nose E, leaving a. flange E between which and the front part of the cap C a space 6* exists asshewnr:

This arrangement causes a suction efi'ect to be producedupontheholes e, e and there fore upon the outer end of the nozzle D during the passage of the projectile through the air. The said nozzle preferably has a divergent cone of 'airangle of fromabout" projectile. suchv as will .give an'- absolute pressure at the outer end of the nozzle Sub. stantially :less thanthe' critical pressure' (about 12.7 lbs. per squarepinch absolute) which suction is produced by suitably (1l.'

mensio ning the partse, E2, E and. in

accordance -with principles which are well understood. Thesaid absolutepressure may be about 11 ,lbs., per square inch As the pressure of the; atmosphere decreases at; high altitudes the'aforesaid' absolute pressure. de-

creases correspondingly and .the aforesaid.

ratio of pressure remains substantially less than the critical ratio. hereinbefore defined. The diameter of. the throatotthe nozzle necessary to enablethe gases to escape as fast as they are genera-tedwilllvary with differ enttypes of powdersbut .with the standard N o. 80 fuse-compositiono-f black powdenthe. composition channel having a CI'QSSr-SQO'. tional area of 1022 square inchand a full burning-time (when the: projectile -is at rest) of about 22v seconds, a diameter of .02975 inch; would be sutficient, wvith a chamber; :of a capacity. of about- 8 v cubic inches, to prevent-rise fpressure in the; chamber. ,Under. these 1 circumstances the T rate xofburning of the fuse composition will be constant-:whatever altitude the shell-may reach. The length of theanozzle isrpr-eferably .37.B=inch-and it has-a flared: entry at, its inner end of about .1 inch radius;v the diverging cone angle-is betweens2 59 and 4,5" as aforesaid. Inviewof spacelimita tionsin "small calibre sh ella re duction i n the gas chamber capacity 1s desirable-,and if a fusecomposit on be used in which the-non- I gaseous products" of combustion .are reducedto a minimum the gascham-bermaybe made substantially smalleryviz, about 2 to' 3 cubic ins. which could bethe .case in; the construe tion illustrated. The largeri-ca-pacity ofv 8 cubic inchespreviously. mentioned is neces sary whenblack powder composition isused,i to allow the nozzle to be placed in a posi- Cojnser tion where the possibilityof foulino from the non-gaseous products of combustion (whrchywith black powder as used in the standard No. fuse;'averageoversfifty per:

centof the total) is unlikely to occur. In any case the interior of the chamber is pref- =erably--made ofthe shape shown .so that the non-gaseous products of combustion will be centrifugallyseparated by theis-pin o f the projectile and l-will settle .in the largest diameter portion of the chamber.

The construction shewn' by Figure. 8- is substantially' the sameas that-above'- .de-

scribed except that a percussion device is incorporated in the rear part of the fuse body, this" device comprising a pellet Ffal detonator capF carried by this pelletand a needle F 'on which thejcapF impinges when the projectile strikes an: obstacle.

Although we have shewn only one nozzle D more than one can be employed in which case the sumof the cross-sectional areas of y the-throats ofthe nozzles should be approximately equal. 1' o the. crosssectional throat area required "for ,a single nozzle.

What I claim and desire to secure by ters Patentof the United States is :v 1. In a p'rojectileltime fuse, the combina tion nvith. a chamber into which pass the gases resulting from theburning of the fuse compositionand an outlet device through which said gases pass-from said chamber to theatmosphere, .of means for subjecting said deviceto a' suction'efiect during the flight of. the projectile so as to produce a ratio betweenthe pressures at theouter end'oi-the deviee and the innerend of the deviee;(i. 'e.l the interior saidchamber) below that Let- V which gives-the maximum velocity of flo wl through saichdeviceathe cross-sectional size of the outlet insa'iddevice being s uch that at this .max-imum velocity the 'gases will escape as fastasthey are generated so that the pressure within the chamber will remain substantially atmospheric, 1

2.111 a projectileytin e fuse, the combination with a chamber into whichipass the gasesresulting from the burning of the fuse composition;- of a nozzle through-which said gases fpa ssl from said rchamber to theatmosphere, means.,for subjecting said nozzle'to-a suction efiect during'the'flight of-thejprojectileso as" to produce a ratio; between the pressure at the outer end of the nozzle and the innermendof the nozzle e. thefinterior of said chamber) below that which gives the maximum velocity of flow-through said 'nozzle. .the cross-sectional area ofthe throat 1 ofs'aid nozzle/being such that at this maxi-.

mum velpcityf the gases will-escape as fast.

as they are generatedso that the pressure within the "chamber will remain substantially atmospheric;

.3. In a .projectiletime, fuse, the combination of a hollow cap mounted in front. of the :2 rev adjustable time ring of the fuse, a nozzle arranged at the front end of said'cap coaxially withrespect to the axis of the projectile, and means for subjecting said nozzle to a suction effect during the flight of the projectile so as to produce a ratio between the pressures at the outer end of the nozzle and the inner end of the nozzle (i. e. the

interior of said cap) below that which gives the maximum velocity of flow through said nozzle, the cross-sectional area of the throat of said nozzle being such that at this maximum velocity the gases will escape as fast as they are generated so that the pressure within the cap will remain substantially atmospheric.

4. In a projectile time fuse, the combination of a hollow cap mounted in front of the adjustable time ring of the fuse, a nozzle arranged at the front end of said cap c0- axially with respect to the axis of the projectile, a nose on the front of said cap for sub ecting said nozzle to a suction efiect dur-o ing the flight of the projectile so as to produce a ratio between the pressures at the outer end of the nozzle and the inner end of the nozzle e. the interior of said cap) below that which gives the maximum velocity of flow through said nozzle, the cross sectional area of the throat of said nozzle being such that at this maximum velocity the gases will escape as fast as they are gen.

erated' so that the pressure within the cap will remain substantially atmospheric,

5. In a projectile time fuse, the combination with the elements claimed in claim 1 and the adjustable element bearingthe fuse 7. In a projectile time fuse, the combination with the elements claimed in claim 3, of an ignition device carried by the adjustable time ring for igniting the fuse composition carried thereby at one end thereof a any setting of said ring.

8. In a projectile time'fuse, the combination with the elements claimed in claim 4,

of an ignition device carried by the adjust- I able time ring for igniting the fuse composition carried thereby at one end thereof at any setting of said ring.

FREDERICK GEOFFREY LEES JOHNSON. 

